The damaging effects of sunlight on skin are well documented. In spite of this, people are forced to be in the sun for long periods of time due to their occupation. Others are in the sun for long periods due to their leisure time activities and/or a desire to have a tanned appearance.
To protect skin from the damaging effects of the sun's rays, sunscreening compositions have been developed which absorb ultraviolet light in the erythemal region. Many of these developments have attempted to improve the substantivity of the sunscreen agent, particularly improving the resistance to being washed off by water. Examples of such compositions are disclosed in U.S. Pat. No. 3,784,488, Jan. 8, 1974 to Steinhauer et al. disclosing organic soluble polymers to form a continuous film on the skin. The polymers are insoluble in the sunscreen agent. Other references disclosing sunscreen compositions containing polymeric materials include U.S. Pat. No. 3,821,363, June 28, 1974 to Black et al. and U.S. Pat. No. 3,895,104, July 15, 1975 to Karg. These compositions all form continuous films with the object being to trap the sunscreen agent on the skin.
Another approach to formulating substantive sunscreen compositions is to use oil soluble polymers along with the sunscreen agent. The polymer does not form a continuous polymeric film but rather, being dissolved in the sunscreen, helps to bind the sunscreen to the skin. One such approach is disclosed in U.S. Pat. No. 4,172,122, Oct. 23, 1979 to Kubik et al. This, as well as the previously described patents, are incorporated herein by reference.
While the prior art suggests numerous methods for improving the performance of sunscreen compositions, there still exists the need for more improvements. One area of desired improvement is in the resistance exhibited by the compositions to being rubbed off. The present inventor has discovered that maintaining the ratio of sunscreen agent to polymer within a certain range provides for improved product rub-off while still maintaining pleasing aesthetics. The polymers used are soluble in the oily, sunscreen material and other oil materials.
In view of the above, it is an object of the present invention to provide effective sunscreen compositions.
It is a further object of the present invention to provide compositions which are resistant to rub-off.
It is still a further object of the present invention to provide sunscreen compositions which have good cosmetic properties (e.g., feel, rub-in, lack of excessive greasiness and/or stickiness, etc.).
These and other objects will become readily apparent from the detailed description which follows.
Unless otherwise indicated, all percentages and ratios herein are by weight.